This project investigates the joint consequences of bilingualism and Alzheimer's disease (AD) for language and cognitive processing, with the goals of shaping psycholinguistic models of bilingualism (Aim 1), testing models of cognitive decline in AD (Aim 2), and characterizing unique aspects in the presentation of bilingual AD (Aim 3). Aging Spanish-English bilinguals are rapidly increasing in numbers in the USA, but almost no information is available on the profile of bilinguals with AD. Using three different models of bilingualism and three models of cognitive decline in AD, we derive specific predictions for the pattern of dual-language decline in bilinguals with AD for several domains (single word production and comprehension, verbal fluency, language switching, cross-language intrusion errors, translation recognition, and management of dual-language activation in sentence reading). Assuming that bilinguals cannot shut a language off, we test the effects of dual-language activation implicitly and explicitly, and examine effects that may be unique to bilinguals with AD (e.g., integrated presentation of language and control deficits, enhanced effects of the option to use either language, reduced cognate and false-friend effects). We hypothesize that AD primarily affects semantic storage in initial stages of the disease and that the dominant language will be more sensitive to such changes. However, we propose that retrieval deficits and language control problems are also present in bilingual AD, and that these deficits will affect the nondominant language with disease progression and in tasks that maximize interference between languages. In each study we consider if the results generalize to early vs. late bilinguals, and unbalanced vs. balanced bilinguals, and the implications of differences across bilingual types. The proposed studies will constrain models of bilingualism and cognitive decline in AD, will reveal the role of control in language processing, and will determine the typical presentation of bilingual AD while also identifying the conditions that allow bilinguals with AD to communicate as fluently as possible.